1. Field of the Invention
This invention relates generally to an alkylation process of aromatic compounds for the production of products such as ethylbenzene and styrene.
2. Description of the Related Art
Styrene is an important monomer used in the manufacture of many of today's plastics. Styrene is commonly produced by making ethylbenzene, which is then dehydrogenated to produce styrene. Ethylbenzene is typically formed by one or more aromatic conversion processes involving the alkylation of benzene in fixed bed or catalytic distillation processes.
Aromatic conversion processes utilizing a fixed bed catalyst are well known in the chemical processing industry. These reactions include the alkylation of aromatic compounds such as benzene to produce alkyl aromatics such as ethylbenzene and also the transalkylation of polyalkyl benzenes to monoalkyl benzenes. In general, such catalysts are selected from molecular sieve catalysts, such as zeolite Y or zeolite beta catalysts, for example.
For liquid phase alkylation processes the alkene fed to the reactor, for example ethylene, should be fully dissolved in the aromatic compound, for example benzene to minimize any deactivation of the liquid phase alkylation catalyst. Typically a large excess of aromatic compound is used to facilitate the dissolving of the alkene and minimize any gas phase alkenes. Any gas phase alkenes that are present can cause rapid deactivation of the typical liquid phase alkylation catalysts. A deactivated catalyst results in the need for regeneration or replacement of the catalyst, which can lead to a reduction in conversion, productivity, and efficiency of the system. In addition any operational upsets to the system can lead to gas phase alkene excursions in the reactor, which can also lead to accelerated catalyst deactivation. Upsets can reduce the run length of the catalyst, catalyst activity, and reduce the period of time between catalyst regeneration, further reducing conversion, productivity, and efficiency.
In view of the above, it would be desirable to have a process of producing alkyl aromatics, such as ethylbenzene, by liquid phase alkylation which is more resistant to any gas phase alkenes that may be present.